Composite nanostructured solid-acid fuel-cell electrodes via electrospray deposition

Stable, porous, nanostructured composite electrodes were successfully fabricated via the inexpensive and scalable method of electrospray deposition, in which a dissolved solute is deposited onto a substrate using an electric field to drive droplet migration. The desirable characteristics of high porosity and high surface area were obtained under conditions that favored complete solvent evaporation from the electrospray droplets prior to contact with the substrate. Solid acid (CsH2PO4) feature sizes of 100 nm were obtained from electrosprayed water-methanol solutions with 10 g L-1 CsH2PO4 and 5 g L-1 Pt catalyst particles suspended using polyvinylpyrrolidone (PVP). Alternative additives such as Pt on carbon and carbon-nanotubes (CNTs) were also successfully incorporated by this route, and in all cases the PVP could be removed from the electrode by oxygen plasma treatment without damage to the structure. In the absence of additives (Pt, Pt/C and CNTs), the feature sizes were larger, similar to 300 nm, and the structure morphologically unstable, with significant coarsening evident after exposure to ambient conditions for just two days. Electrochemical impedance spectroscopy under humidified hydrogen at 240 degrees C indicated an interfacial impedance of similar to 1.5 Omega cm(2) for the Pt/CsH2PO4 composite electrodes with a total Pt loading of 0.3 perpendicular to 0.2 mg cm(-2). This result corresponds to a 30-fold decrease in Pt loading relative to mechanically milled electrodes with comparable activity, but further increases in activity and Pt utilization are required if solid acid fuel cells are to attain widespread commercial adoption.